An analysis released Tuesday by the National Center for Education Statistics found that students who took out federal loans but later dropped out had a median federal debt load equal to 35 percent of their annual income, and that dropouts from for-profit colleges borrowed the most per credit earned: $350 per credit, compared with less than $120 per credit for students in other sectors. The report looked at student debt for students who enrolled in college in the 2003-04 academic year but did not complete within six years. It also found that 21 percent of noncompleters from four-year private nonprofit colleges, and 31 percent of students from for-profit colleges who did not earn a credential, had student loan debt greater than their annual income.